Originally posted by chromius_e30 I would have to disagree....I would not put a straight fill of antifreeze, otherwise you would have to replace it when the summer comes along....antifreeze has less cooling properties than just straight water, and in the hot summer months the engine temp would be much higher than it should be. a 50/50 mix is good down till -35 degrees celcius. if need be change the mix to 60% antifreeze to 40% water, and this will be good enough for the coldest of days....but in the summer you might notice an increase in temp. for most applications a 50/50 mix is just perfect though. In hot summer months a lot of high load engines use 10% antifreeze to 90% water to prevent overheating.

just a thought.

I always drained my anti-freeze come summer time but for people that dont,60/40 mix is good for the winter.